1. Field of the Invention
The present invention relates to a webbing retracting device that takes up and stores a long band-shaped webbing belt that restrains the body of an occupant of a vehicle.
2. Description of the Related Art
Seatbelt devices for restraining the body of an occupant by a long band-shaped webbing belt are provided with a webbing retracting device. Such a webbing retracting device is provided with a spool. The webbing belt is attached to the spool at a longitudinal direction proximal end side thereof, and when the spool is rotated in a take up direction around its axis, the webbing belt is wound up from the proximal end side and stored on the spool.
In a webbing retracting device, a lock mechanism is provided for locking the spool when there is a sudden vehicle deceleration or the like, restricting pull out of the webbing belt, and holding the body of an occupant attempting to move in a direction that is substantially toward the front of the vehicle (see, for example, Japanese Patent Application Laid-Open (JP-A) No. 5-208655).
In the webbing retracting device disclosed in JP-A No. 5-208655, a lock gear is provided that is rotatable coaxially with respect to a reel shaft (spool). Between the lock gear and the spool, a pawl (interlocking member) interlocks the lock gear and the spool, and when the spool relatively rotates with respect to the lock gear in the webbing pull out direction, the interlocking member is displaced toward the outside in the rotational radial direction of the spool, and mesh with a ratchet of internal teeth formed on a frame. In this way the spool is locked and rotation of the spool when the webbing belt is pulled out is restricted.
Furthermore, in the lock gear there is an inertial member (mass) supported so as to be able to relatively pivot with respect to the lock gear, and when the lock gear rotates at a normal speed the mass follows and rotates. However, when the lock gear is rotated suddenly the mass undergoes inertial movement and relatively pivots with respect to the lock gear, displacing toward the outside in the lock gear rotational radial direction, meshing with the ratchet of internal teeth formed on the frame. By doing so, the lock gear is locked and only the spool rotates.
That is, in normal pulling out and taking up of a webbing belt, the lock gear rotates, following with respect to the rotation of the spool. However, under conditions of sudden deceleration, the body of an occupant moves in a substantially forward direction, and due to this, the webbing belt is pulled out suddenly, and, when the spool is rotated suddenly in the pull out direction, the lock gear locks, and the spool rotates in the pull out direction with respect to the lock gear. By doing so, as described above, the interlocking member meshes with the ratchet of the frame, the spool is locked, and pulling out of the webbing belt is restricted.
Here, the mechanism is complicated for detecting the condition in which the webbing belt is pulled out suddenly from the spool, with an interlocking member being used in order to couple the spool and the lock gear rotation, and a joint pin being used to interlock the pawl to the spool and to the lock gear, and guide grooves being formed to guide the lock pawl and joint pin to the spool and the lock gear, and so on. This has the problem that the cost is high.